Some families of two-winged flies, Diptera, have been the subject of detailed research by the Liverpool Musem and in the case of the Robber Flies, Asilidae, 40 different species have been found on the island though all have not yet been named , due to the need for taxanomic revision within the family. Three potentially new species have been found, currently subject to further study.

Two specimens of a rare species of Robber Fly, Andrenosoma cornuta, were discovered at Elinta and Agiasmata in 1997, the first Greek and European records, these were found close to the beaches at both sites. This species was described fifty years ago from three immature specimens taken in Turkey. No further specimens were seen until their rediscovery on Chios. The insect was not found in these two sites despite repeated searches in subsequent years. Fortunately in September 2002 a small colony was discovered on the coast just to the north of Gridia. A paper will be published in due course describing the habitat requirements and courtship and hunting behaviour of this species following further research on this colony.

An extraordinary attack by a large Robber Fly of the genus Stenopogon, ( species probably junceus ), was observed and photographed at Kato Fana where the prey species was a very large Antlion, Palpares libelluloides. This was unusual in that the span of the prey was four times larger than that of the predator. Because the predator is usually much larger than the prey in the Asilidae, photographs of the attack were of great interest to researchers into Robber Fly behaviour in the U.S.A.

Some Hover Fly, Syrphidae, genera have been the subject of detailed study on Chios where the range of available foodplants is particularly large and has the potential of hosting a large number of species . The genus Merodon is represented by fifteen species on the island. This genus includes a number of large, noticeable and attractive species which are sure to draw the attention of the naturalist because of their active and intrusive territorial defense behaviour. These insects can be found throughout the island wherever their foodplants occur. The larvae of this family feed on plants with bulbs or tuberous roots.

Some rare species of Merodon have been discovered on Chios including Merodon
toscanus, which was described by the Dutch entomologist Hurkmans in 1993 from a single male specimen which he had taken in Italy. The single male taken in June 2001 between Armolia and Tholopotami being the second known specimen. Another rare species, Merodon hamifera, has been discovered on Chios with two males at Amahdes and a single male in Leptopoda. These were the first records since the original specimens were taken in Turkey over a hundred years ago and a single specimen was taken in Samos about seventy years ago. Colleagues from the U.K. and I have recently discovered a strong colony of this fly at Ag Iassos in Lesvos.

Two potentially new species of Merodon have been found on Chios and these are the subject of further study with the intention of publishing descriptions in due course. The early stages of many of the species occurring on Chios have unknown foodplants and their larvae have never been identified. The discovery of their foodplants and the preparation of detailed descriptions of the early stages would make a good project for a student of natural history on the island.

In April and May, insects which look like wasps may be seen nectaring on the spring flowers and are also to be seen flying slowly close to the ground amongst vegetation alongside country footpaths. Some of these insects are not wasps, they are Hoverflies which mimic them. This strategy protects them from potential predators who mistake them for wasps which have to be avoided. So far two species of flies of the genus Xanthogramma have been found on Chios. The photograph shows a female of X. citrofasciatum nectaring on a flower near Pagida early in April. Females seek out colonies of ants of the genus Lasius, these ants tend and protect underground 'herds ' of root aphids from which they receive sugary honeydew secretions in return for protection by these ants from their predators. However the larvae of Xanthogramma have developed methods to defeat the ants protection and successfully feed upon the aphids. Many other species of Hoverflies from many different genera also prey on aphids in their larval stages but these feed on different species of aphids in quite different ways.

A number of interesting Horse Flies, Tabanidae, have been found in Chios including a very rare endemic Greek species, Haematopota graeca . This species was described by the Hungarian entomologist, Szilady, from three specimens taken on Poros, however they were all lost when the museum in Budapest was destroyed during the Hungarian uprising in 1956. It had not been seen subsequently until its recent rediscovery at Kato Fana. It occurs in small numbers in the area immediately behind the beach, mainly in September and October and very occasionally in May. In the last six years an average of three specimens have been seen per year. They seem to be most common following wet winters.

Specimens of a large species of Horse Fly Tabanus prometheus, have been taken occasionally in north and central Chios, this species was previously known only from Transcaucasus, Iran and Bulgaria. One of the commonest species seen in June is
Tabanus lunatus, which occurs widely throughout the Mediterranean region. The
females of this species readily seek blood from animals and humans, the females have bright green eyes with three lateral bands, bright magenta in colour. These insects can occur in large numbers and can cause serious loss of condition in animals such as horses, donkeys and cattle due to blood loss. In June 2001 I found a white cow tethered in a field to the west of Pitios, its legs were covered with hundreds of T.lunatus and one T.prometheus, as a result of this mass attack all of its legs were running with blood upon which the swarm of Horse Flies were feeding.

There are accounts of this behaviour in Africa, however this was the first time I have witnessed such an event. At the same time I noticed some donkeys in the village also attracting numbers of the same species of Horse Fly. Some villagers in Viki recently related to me the case of a donkey in the village which had died of blood loss as a result of a similar attack. An investigation into these attacks in central Europe has shown that mass attacks peak at around 11am, the time I witnessed the Pitios attack, to be followed by a second attack at around 2pm. The literature on these flies indicate that these attacks usually follow a mass emergence at a time of very hot, calm and humid weather conditions. The females require a blood meal in order to mature and develop their eggs which are laid in the ground, 400 to 1000 eggs per female, often near or in aquatic or damp situations, they only seek blood after mating. The larvae are predatory, feeding in the soil on worms, molluscs and predominantly on the larvae of other Diptera.

There is another small family of flies, the Conopids, Conopidae, which have a very interesting life history. These flies prey on species of bees and wasps, Hymenoptera, many of the adults mimic the shapes and colours of their prey. One of the most noticeable in Chios is Conops flavicauda, which looks like a much thinner version of the familiar Oriental Hornet, Vespa orientalis. These two species share the same colour scheme of warm brown and yellow body colours and light brown / yellowish wings. They are widespread in Chios in late June through August and can be seen nectaring on umbelliferous plants such as Rock Samphire, Crithmum maritimum, in coastal locations. Conopid females loiter around wild flower nectar sources waiting to pounce on visiting bees and wasps.

In an attack an aerial wrestling match ensues, not always won by the attacker, in a successful encounter the Conopid inserts one of its thin barbed eggs into one of the segments of the victims abdomen using its piercing ovipositor. After the combatants disengage, the unsuspecting victim goes about its normal business unaware that it is doomed. The egg soon hatches and the small larva proceeds to eat the body tissues within the abdomen of the host. The larva passes through a number of stages following which the victim eventually succumbs to the attack and falls to the ground. The parasite pupates within or adjacent to the victims body, to emerge as an adult in the following season. I have found this species commonly on the north coast at Yiosonas and at Kampia Beach and at coastal locations on the west and south coasts. To date seven species of Conopid have been found on Chios.